Food contact grade water-based VAE adhesive for PE coated kraft paper as well as preparation method and application of food contact grade water-based VAE adhesive

Abstract

The invention discloses a food contact grade water-based VAE adhesive for PE coated kraft paper as well as a preparation method and application of the food contact grade water-based VAE adhesive, and belongs to the technical field of polymer adhesives. The water-based VAE adhesive is prepared from the following components in percentage by mass: 1%-50% of a DiverSol540 VAE emulsion, 30%-90% of a DiverSol613M VAE emulsion, 1%-35% of emulsified water-based rosin and 1%-10% of water. The water-based VAE adhesive disclosed by the invention can form high-strength combination with kraft paper fibers, simultaneously realizes excellent initial wetting and firm adhesion to high-gram-weight PE coated kraft paper, has good cohesion and heat resistance, can effectively prevent thermal creep in a high-temperature coating process or in subsequent use, and solves the problem of high-end food packaging.

Description

Technical Field

[0001] This invention belongs to the field of polymer adhesive technology, specifically a food-contact grade waterborne VAE adhesive for PE-coated kraft paper, its preparation method, and its application. Background Technology

[0002] Polyethylene (PE) coated kraft paper combines the mechanical strength and printability of paper substrates with the waterproof, oil-proof, and heat-sealing properties of PE film, making it widely used in various packaging applications. Its performance hinges on the bonding strength between the PE coating layer and the kraft paper substrate. However, as a difficult-to-bond material, it suffers from several challenges. Firstly, the low surface energy of the PE coating makes adhesive adhesion difficult. Secondly, the high grammage of kraft paper presents challenges such as poor penetration, difficulty in folding, and high resilience. Traditional adhesives, such as general-purpose VAE emulsions or acrylic emulsions, often suffer from insufficient adhesion to non-polar PE surfaces, poor resistance to high temperatures and humidity, insufficient cohesion, and poor formulation stability when used at this interface. These issues lead to delamination, blistering, and other failures in the composite material under humid and hot conditions or with fluctuating temperatures.

[0003] Existing technologies often improve adhesive properties by adding coupling agents, plasticizers, tackifying resins, or crosslinking agents. However, these methods suffer from problems such as complex formulations, increased production costs, and reduced environmental and food contact safety. VAE emulsions, due to their good affinity for cellulose substrates and excellent film-forming flexibility, are ideal base materials for paper-plastic composite adhesives. However, different manufacturers and models of VAE emulsions exhibit significant differences in vinyl acetate content, emulsion systems, particle sizes, glass transition temperatures, and types of functional monomers. This directly leads to significant fluctuations in their double-sided adhesion performance, moisture and heat resistance, and system stability between PE and paper substrates. Conventional general-purpose VAE emulsions are difficult to simultaneously meet the composite requirements of PE-coated kraft paper.

[0004] Therefore, it is of great significance to screen and compound VAE emulsions with specific performance parameters to solve the industry pain points of PE-coated kraft paper composite bonding, without relying on a large amount of external modified additives and ensuring environmental protection and economy. Summary of the Invention

[0005] To address the shortcomings of the existing technology, the purpose of this invention is to provide a food-contact grade water-based VAE adhesive for PE-coated kraft paper. This water-based VAE adhesive exhibits ultra-high initial adhesion and excellent final peel strength to PE coatings. PE-coated kraft paper packaging boxes prepared using this adhesive possess high peel strength and excellent weather resistance, are environmentally friendly and safe, and are suitable for high-end packaging materials such as food products, demonstrating significant industrial value.

[0006] To achieve the above objectives, the specific technical solution of the present invention is as follows:

[0007] A food-contact grade waterborne VAE adhesive for PE-coated kraft paper comprises the following components by weight percentage: 1%~50% DiverSol® 540 VAE emulsion, 30%~90% DiverSol® 613M VAE emulsion, 1%~35% emulsified waterborne rosin, and 1%~10% water.

[0008] This invention combines two functional VAE emulsions, DiverSol® 540 and DiverSol® 613M, and introduces emulsified waterborne rosin as a natural tackifier. This allows for excellent wetting and strong adhesion to non-polar PE surfaces without relying on complex additive systems. At the same time, it forms a high-strength bond with kraft paper fibers, resulting in an environmentally friendly adhesive with ultra-high initial adhesion and excellent final peel strength to PE films, as well as excellent cohesion and weather resistance. DiverSol® 540 VAE has a Tg of -3 to 5°C, providing sufficient cohesive strength to the adhesive and improving its heat resistance. It also offers excellent penetration and anchoring to porous kraft paper substrates, ensuring superior adhesion. DiverSol® 613M has a Tg of -40 to -30°C and contains various functional monomers, exhibiting strong wetting power on low surface energy substrates and providing robust adhesion to such materials. In composite systems, the polymer segments of DiverSol® 613M migrate more effectively to the PE surface and adhere tightly, forming a strong transition layer between the PE and the adhesive layer. Furthermore, its high molecular weight and high cohesive strength ensure strong cohesion in the formulated adhesive, thus its addition to DiverSol® 540 VAE does not affect the adhesive's cohesive strength. Emulsified waterborne rosin significantly improves the initial tack of adhesives. It also exhibits good compatibility with DiverSol® 540 and DiverSol® 613M emulsions, optimizing the balance between cohesive strength and toughness of the adhesive film and providing some water resistance. Through the interaction of DiverSol® 540, DiverSol® 613M, and emulsified waterborne rosin, an environmentally friendly adhesive can be obtained that does not rely on complex additives, exhibits extremely high adhesion to kraft paper and PE films, and possesses excellent cohesive strength and weather resistance.

[0009] Preferably, the DiverSol® 540 VAE emulsion has a mass percentage of 5% to 40%.

[0010] Preferably, the DiverSol® 613M VAE emulsion has a mass percentage of 40% to 70%.

[0011] Preferably, the mass percentage of the emulsified water-based rosin is 10% to 30%.

[0012] Preferably, the viscosity of the water-based VAE adhesive is 1000~8000 mPa•s, and the solid content is 45%~60%.

[0013] Another object of the present invention is to provide a method for preparing the food contact grade waterborne VAE adhesive, comprising the following steps: mixing the DiverSol® 540 VAE emulsion and the DiverSol® 613M VAE emulsion evenly, then slowly adding the emulsified waterborne rosin under stirring, homogenizing, and then adding water to obtain the final product.

[0014] Preferably, the preparation method specifically includes the following steps:

[0015] Weigh each component by mass percentage, add the DiverSol® 540 VAE emulsion to a mixing container, add the DiverSol® 613M VAE emulsion at 200-400 rpm, continue stirring for 20-60 min, then increase the stirring speed to 600-800 rpm, add the emulsified water-based rosin while stirring, and continue stirring for 20-60 min to form a stable composite emulsion system;

[0016] Add water at 200-400 rpm to adjust the viscosity and solid content of the system, and then filter it through a 100-150 mesh filter to obtain the water-based VAE adhesive.

[0017] Another object of the present invention is to provide the application of the water-based VAE adhesive in food contact materials.

[0018] Preferably, the food contact material is PE-coated kraft paper.

[0019] Preferably, the application method is as follows: the water-based VAE adhesive is coated onto the PE film surface, and the dry adhesive coating amount is 10~50g / m². 2 Then cover it with kraft paper.

[0020] Compared with the prior art, the advantages of the present invention are:

[0021] (1) The water-based VAE adhesive of the present invention can form a high-strength bond with kraft paper fibers, and at the same time achieve excellent initial wetting and firm adhesion to high grammage PE coated kraft paper, solving the problem of high-end food packaging.

[0022] (2) The water-based VAE adhesive of the present invention has good cohesion and heat resistance, which can effectively prevent thermal creep during high-temperature coating process or subsequent use.

[0023] (3) The water-based VAE adhesive of the present invention has suitable rheological properties and meets the process requirements of high-speed coating.

[0024] (4) The water-based VAE adhesive of the present invention adopts a fully water-based system, which is environmentally friendly, safe to produce, and can be used in food packaging materials. Detailed Implementation

[0025] The technical solution of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] The food-contact grade waterborne VAE adhesive for PE-coated kraft paper of the present invention comprises the following components in weight percentage: 1%~50% DiverSol® 540 VAE emulsion, 30%~90% DiverSol® 613M VAE emulsion, 1%~35% emulsified waterborne rosin, and 1%~10% water.

[0027] In some embodiments, the waterborne VAE adhesive comprises the following components in weight percentages: 5%~40% DiverSol® 540 VAE emulsion, 40%~70% DiverSol® 613M VAE emulsion, 10%~30% emulsified waterborne rosin, and 1%~10% water.

[0028] The water-based VAE adhesive of the present invention has a viscosity of 1000~8000 mPa•s at 25°C and a solid content of 45%~60%.

[0029] In the following examples and comparative examples, DiverSol® 540 VAE emulsion, DiverSol® 613M VAE emulsion, and DiverSol® 320 VAE emulsion were all provided by Yunnan ZhengBang Technology Co., Ltd. Specifically, the DiverSol® 540 VAE emulsion had a solid content ≥55%, a viscosity range of 3500~5000 mPa•s, and a Tg of -3~5℃; the DiverSol® 613M VAE emulsion had a solid content ≥58%, a viscosity range of 5000~10000 mPa•s, and a Tg of -40~-30℃; and the DiverSol® 320 VAE emulsion had a solid content ≥55%, a viscosity range of 500~2000 mPa•s, and a Tg of -15~-10℃. The emulsified waterborne rosin was provided by Guangxi Wuzhou Huangchuan Chemical Industry Co., Ltd.

[0030] Example 1

[0031] The water-based VAE adhesive of this embodiment is composed of the following components by weight percentage: 17% DiverSol® 540 VAE emulsion, 68% DiverSol® 613M VAE emulsion, 13% emulsified water-based rosin, and 2% deionized water;

[0032] The preparation method of the water-based VAE adhesive in this embodiment specifically includes the following steps:

[0033] Weigh each component by mass percentage, add the measured amount of DiverSol® 540 VAE emulsion to a mixing tank, add DiverSol® 613M VAE emulsion while stirring at a low speed of 200~400 rpm, continue stirring for 30 min until uniformly mixed, then increase the stirring speed to 600~800 rpm, and add the emulsified water-based rosin while stirring. This process should be completed within 30~45 min to ensure that the two emulsions are fully homogenized and form a stable composite emulsion system.

[0034] Reduce the stirring speed to 200-400 rpm, add deionized water to adjust the viscosity and solid content of the system, and then filter it through a 100-mesh filter to obtain the above-mentioned water-based VAE adhesive.

[0035] Example 2

[0036] The water-based VAE adhesive of this embodiment is composed of the following components by weight percentage: DiverSol® 540 VAE emulsion 34%, DiverSol® 613M VAE emulsion 51%, emulsified water-based rosin 13%, and deionized water 2%.

[0037] The preparation method of the water-based VAE adhesive is the same as in Example 1.

[0038] Example 3

[0039] The water-based VAE adhesive of this embodiment is composed of the following components by weight percentage: 1% DiverSol® 540 VAE emulsion, 90% DiverSol® 613M VAE emulsion, 7% emulsified water-based rosin, and 2% deionized water;

[0040] The preparation method of the water-based VAE adhesive is the same as in Example 1.

[0041] Example 4

[0042] The water-based VAE adhesive of this embodiment is composed of the following components by weight percentage: 40% DiverSol® 540 VAE emulsion, 30% DiverSol® 613M VAE emulsion, 28% emulsified water-based rosin, and 2% deionized water;

[0043] The preparation method of the water-based VAE adhesive is the same as in Example 1.

[0044] Comparative Example 1

[0045] The waterborne VAE adhesive of this comparative example is composed of the following components by mass percentage: 85% DiverSol® 613M VAE emulsion, 13% emulsified waterborne rosin, and 2% deionized water; the preparation method of the waterborne VAE adhesive is the same as in Example 1.

[0046] Compared to Example 1, this comparative example omits DiverSol® 540 VAE emulsion and correspondingly increases the amount of DiverSol® 613M VAE emulsion.

[0047] Comparative Example 2

[0048] The waterborne VAE adhesive of this comparative example is composed of the following components by mass percentage: 85% DiverSol® 540 VAE emulsion, 13% emulsified waterborne rosin, and 2% deionized water; the preparation method of the waterborne VAE adhesive is the same as in Example 1.

[0049] Compared to Example 1, this comparative example omits DiverSol® 613M VAE emulsion and correspondingly increases the amount of DiverSol® 540 VAE emulsion.

[0050] Comparative Example 3

[0051] The water-based VAE adhesive in this comparative example is basically the same as that in Example 1, except that the DiverSol® 613M VAE emulsion is replaced with an equal amount of DiverSol® 320 VAE emulsion.

[0052] Comparative Example 4

[0053] The water-based VAE adhesive of this comparative example is composed of the following components by mass percentage: 98% DiverSol® 540 VAE emulsion and 2% deionized water; the preparation method of the water-based VAE adhesive is the same as in Example 1.

[0054] Compared with Comparative Example 2, this comparative example omits the emulsified water-based rosin and correspondingly increases the amount of DiverSol® 540VAE emulsion.

[0055] The viscosity and solid content of the waterborne VAE adhesives prepared in each embodiment and comparative example are shown in Table 1.

[0056] Table 1. Viscosity and Solid Content of Water-Based VAE Adhesives

[0057]

[0058] Application examples

[0059] The aqueous VAE adhesive prepared in the examples and comparative examples was applied to PE-coated kraft paper, and the process is as follows:

[0060] S1. Apply the adhesive evenly to the PE film surface using reverse roller coating or micro-gravure coating methods, with a dry adhesive coating amount of 10~50g / m². 2 ;

[0061] S2. Fold the glued cardboard along the creases to ensure close contact between the glued surface and the kraft paper surface; immediately after folding, apply pressure to shape it by using a pressure pulley to apply continuous pressure to ensure that the glue layer is fully bonded to the paper surface;

[0062] Performance testing

[0063] 1. PE adhesion test

[0064] 1.1 Substrate: 250g / m 2 Kraft paper and PE film.

[0065] 1.2 Apply the corresponding thickness of glue to the kraft paper using the corresponding bar, cover with PE film, press with rollers, and cure for 24 hours; the PE adhesion test results are shown in Table 2.

[0066] Table 2 PE adhesion test results

[0067]

[0068] 2. Wet adhesion and bond strength test

[0069] 2.1 Substrate: 250g / m 2 PE coated kraft paper

[0070] 2.2 Apply adhesive to a concentration of 250 g / m using a dispensing method. 2 For the coated surface of coated kraft paper, adhere another coated kraft paper to it, press for 5 seconds, and then quickly tear it apart after 2 minutes. Observe whether the material is damaged or paper fibers are stuck together. At the same time, perform a slow tear test. Prepare samples in the same way, cure for 24 hours, and then tear them apart quickly and slowly to observe whether the material is damaged; material damage refers to the destruction of kraft paper fibers. The wet tack test results are shown in Table 3.

[0071] Table 3 Results of wet tack test

[0072]

[0073] 3. Weather resistance test

[0074] The high temperature and high humidity resistance was tested according to CY / T 224-2020 "Requirements and Test Methods for Adhesives for Folding Paper Boxes" 4.2.6. The test results are shown in Table 4.

[0075] Table 4 Weather resistance test results

[0076]

[0077] As can be seen from the data in Tables 2-4, the water-based adhesive of the present invention exhibits high adhesion to PE materials, excellent bonding ability to PE interfaces, and can form a high-strength bond with kraft paper fibers, achieving a material-destructive effect, while also demonstrating excellent weather resistance. A comparison of Examples 1 and 2 reveals that increasing the amount of DiverSol® 613M VAE emulsion significantly improves the adhesion of the adhesive to PE materials without sacrificing cohesion, thus achieving the same material-destructive effect.

[0078] Comparing Example 1 and Comparative Example 1, it can be found that while using only DiverSol® 613M VAE emulsion can improve adhesion to PE materials, the weather resistance test is not passed. Comparing Example 1 and Comparative Example 2, it can be found that using only DiverSol® 540 VAE emulsion significantly reduces adhesion to PE materials. This indicates that compared to using DiverSol® 540 VAE emulsion or DiverSol® 613M VAE emulsion alone, using a combination of DiverSol® 540 VAE emulsion and DiverSol® 613M VAE emulsion can improve the adhesion of the adhesive to PE materials, enhance the bonding effect of the adhesive to the PE interface, and improve the weather resistance and tolerance of the adhesive to high temperature and high humidity environments.

[0079] Examples 1 and 3 show that replacing DiverSol® 613M VAE emulsion with an equal amount of DiverSol® 320 VAE emulsion fails to achieve excellent adhesion to high-basis-weight PE-coated kraft paper, resulting in a significant decrease in adhesive performance. Further comparisons of 2 and 3 reveal that adding DiverSol® 320 VAE emulsion to the formulation, compared to using DiverSol® 540 VAE emulsion alone, only slightly improves the adhesion of the adhesive to the PE material, with a very limited improvement.

[0080] In summary, this invention provides a highly simple, environmentally friendly, and high-performance adhesive specifically for PE-coated kraft paper by carefully selecting and compounding two complementary VAE emulsions, DiverSol® 540 and DiverSol® 613M, produced by Yunnan ZhengBang Technology Co., Ltd., and further optimizing performance with emulsified water-based rosin. The core of this technology lies in utilizing the specific high adhesion of DiverSol® 613M to PE materials, overcoming traditional bonding challenges. By adjusting its dosage, the peel strength of the final product can be directly and effectively controlled, solving a key technical bottleneck of traditional adhesives in this application and possessing significant industrial production value. It should be noted that the storage temperature of this adhesive is 5~40℃, and the operating temperature is 15~30℃. Operating temperatures below 8℃ may have a certain impact on bonding performance.

[0081] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A food-contact grade water-based VAE adhesive for PE-coated kraft paper, characterized in that, The components include the following percentages by weight: DiverSol® 540 VAE emulsion 1%~50%, DiverSol® 613M VAE emulsion 30%~90%, emulsified waterborne rosin 1%~35%, and water 1%~10%.

2. The food-contact grade water-based VAE adhesive for PE-coated kraft paper according to claim 1, characterized in that, The DiverSol® 540 VAE emulsion has a mass percentage of 5% to 40%.

3. The food-contact grade water-based VAE adhesive for PE-coated kraft paper according to claim 1, characterized in that, The DiverSol® 613M VAE emulsion has a mass percentage of 40% to 70%.

4. The food-contact grade water-based VAE adhesive for PE-coated kraft paper according to claim 1, characterized in that, The emulsified water-based rosin has a mass percentage of 10% to 30%.

5. The food-contact grade water-based VAE adhesive for PE-coated kraft paper according to claim 1, characterized in that, The viscosity of the water-based VAE adhesive is 1000~8000 mPa•s, and the solid content is 45%~60%.

6. A method for preparing the food contact grade waterborne VAE adhesive according to any one of claims 1 to 5, characterized in that, Includes the following steps: The DiverSol® 540 VAE emulsion and the DiverSol® 613M VAE emulsion are mixed evenly, and then the emulsified water-based rosin is slowly added while stirring to homogenize. Water is then added to obtain the final product.

7. The use of the water-based VAE adhesive according to any one of claims 1 to 5 in food contact materials.

8. The application according to claim 7, characterized in that, The food contact material is PE-coated kraft paper.

9. The application according to claim 8, characterized in that, The water-based VAE adhesive is coated onto the PE film surface, with a dry coating amount of 10~50g / m². 2 Then cover it with kraft paper.

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